The present invention relates to a method of cooling by air or other gas, hot cement clinker, lime and the like that is burned or sintered by a cement burning device such as a rotary kiln, as well as a clinker cooling apparatus.
Normally, cement clinker sintered by a cement burning apparatus such as a rotary kiln is cooled by air or other gas flowing upwardly from below a grate through a layer of clinker formed from clinker falling on a grate-type cooling apparatus under high temperature conditions of about 1,300.degree. C. In view of thermal economy, it is desirable to recover as much of the heat retained in the hot clinker fallen on the cooling apparatus as possible and to obtain as high a temperature exhaust gas as possible, because there are frequent cases where a part of the exhaust gas from such cooling apparatus is used in the burning apparatus as secondary air. Thus, the clinker layer formed in the cooling apparatus must be made into a distributed and uniformally thick layer.
However, since the clinker particle distribution rayers from particles finer than 1 mm to large lumps of more than 100 mm, and further since the clinker is discharged from a limited portion of the rotary kiln, it piles up on the grate to form a small hill, so that the thickness and particle sizes of the clinker layer are uneven or sometimes resulting in variations in particle size, temperature and amount of clinker from the rotary kiln. Thus, for the above mentioned reasons, the resistance to the cooling air differs according to time or position, resulting in uneven cooling to cause reductions in exhaust gas temperature and the phenomenon of raised clinker temperatures at the outlet of the cooling apparatus. Also, the thickness of the clinker layer at both ends of the clinker layer, that is, the thickness of the clinker layer at both ends of the clinker layer widthwise in the cooling apparatus is thinner than the thickness of the central portion thereof, and fine particles are condensed to cause the upward and downward mixing of the clinker layer fluidized by the cooling air, so that such disadvantageous as reductions of the exhaust gas temperature in the upper portion of the clinker layer are caused.
The apparatus is generally operated so that thickness of the clinker layer is within the range of about 300-700 mm, although it is desirable that the layer thickness be within 1,000-2,000 mm in view of heat recovery. However, in this event, troubles occur such as delays in cooling the upper portion of layer to cause sintering between the clinker particles, making movement of the clinker layer in the longitudinal direction difficult, and thus it is necessary that the apparatus be operated with a clinker layer thickness of about 300-700 mm.